Batch Load Using DynamoDB Mapper (Guide w/ Code Examples)

You can use the DynamoDB mapper's batchLoad method to load multiple items from a DynamoDB table.

We first build a list of primary key values for the items we want to retrieve from the DynamoDB table. Then we create a DynamoDBQueryExpression object and set the primary key values using the withKeys method. We pass this query expression to the batchLoad method along with the class of the item we are loading, and it will return the list of items that match the primary keys.

import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBQueryExpression;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class DynamoDBMapperBatchLoadExample {
    public static void main(String[] args) {
        AmazonDynamoDB client = AmazonDynamoDBClientBuilder.defaultClient();
        DynamoDBMapper mapper = new DynamoDBMapper(client);

        List<String> ids = Arrays.asList("1", "2", "3");
        List<Object> keys = new ArrayList<Object>();
        for (String id : ids) {
            Item item = new Item();
            item.setId(id);
            keys.add(item);
        }

        DynamoDBQueryExpression<Item> queryExpression = new DynamoDBQueryExpression<Item>().withKeys(keys);
        List<Item> items = mapper.batchLoad(Item.class, keys);

        System.out.println("Items retrieved successfully!");
        System.out.println(items);
    }
}